Paving apparatus and method



w. M. VENABLE 2,145,959

PAVING APPARATUS AND METHOD Feb. 7, 1939.

5 Sheets-Sheet 1 Filed Jan. 24, 1936 IPJVENTORY Feb. 7, 1939. w. M. VENABLE' PAVING APPARATUS AND METHOD Filed Jan. 24, 1936 s Sheets-Sheet 2 Feb. 7, 1939. w. M. VENABLE PAVING APPARATUS AND METHOD File d Jan. 24, 19:6 5 Sheets-Sheet :s

INVENTOR Feb. 7, 1939. w. M. VENABLE 2,145,959

PAVING APPARATUS AND METHOD Filed Jan. 24, 1936 5 Sheefcs-Sheet 4 II II I I I I I I m 1 II N I I I I; I I I I I I- v I M I I I I I I I I I KI I i i Q 3| I u I II I 0, Q *3 3; 3 w Ig I n I 3 I I I N H I I I I hm II I I I l I; I'=== I,I I I I ./'\-I\| I I I II I IQF I I II- I III I N II? I I\ III 'l II I I I k I I I I I I I I II I I- I-I I I I II |I II I I N I I I II I I0 I II II I' II II I I I I I 33 II II I I I: l -I\ N a N I II I II I I "I 3 II I I II I I I I II I III I} I I g I- I I, I I I I I III II III II III N I| II I II I I I I I I I II I I N J I .I "I I; I IP BI II I I I m I w i I'II l I N :JI\\ Q I ix: :5 "III I I s III: I I I I=7 I III I I I I I 3 L I I D u I I I I N INVENTOR Er II N I I J I I I II N $7 $7 I II I I I I I I a M I M PAVING AIQPARATUS AND METHOD Filed Jan. 24, 1936 5 Sheets-Sheet 5 l z 21 2 I I Io Patented Feb; 7, 1939 UNITED STATES PATENT OFFICE PAVING APPARATUS AND METHOD Application January 24, 1936, Serial No. 60,615

'24 Claims.

This invention relates to paving and particularly to a method and apparatus for finishin roadways formed of initially plastic material such as concrete.

In the construction of roadways of concrete, for example, a sub-grade is first prepared and freshly mixed concrete deposited thereon between road rails or forms defining the edges of the slab to be formed. Various types of apparatus for finishing the surface of the concrete slab have been proposed heretofore, to avoid the hand finishing which was employed in the early days of concrete road construction. A common feature of finishing machines in general use, is a 15. screed, the ends of which rest upon the road rails. Each screed has a front surface to push forward surplus concrete, and a bottom surface to work upon the upper surface of the concrete slab. Screeds are reciprocated" longitudinally while being moved forward, pushing surplus concrete in front of them, the weight of which surplus concrete tends to compact the other con- 1 is utilized in massive masonry construction, and

obtaining the des red compacting of the concrete. Certain road finishing machines, e. g. as shown in my prior Patent No. 1,887,341, are capable of working concrete of a somewhat reduced plasticity but even a machine of the type 40 shown in the patent requires that the concrete be sufliciently plastic to permit two successive screedings. The usual practice in operating screeding machines has been to move the machine over the work more than once, leaving a comparatively smooth but a slightly high surface the first time and then removing the surplus height by subsequent passes.

Such machines are objectionable not only because the necessity for two passes limits the use thereof to concrete having relatively high plasticity but also because it is practically impossible to obtain a slabv of uniform thickness.

Concrete as deposited infront of the machine is not perfectly distributed over the width of the u road and as the machineadvances the heightv of the concrete pile pushed forward in front of the screed varies from point to point along the screed. Consequently, even if the concrete be of uniform consistency, the amount which fiows beneath the screed varies from point to point, 5 and the concrete left after each pass is neither perfectly graded nor uniformly compacted. Variations in plasticity increase the unevenness, as they occasion unequal settling after the finishing machine has completed its work, some settling being unavoidable with the mixtures such machines are capable of placing.

It is obviously impossible, with machines such as known heretofore, to work concrete having a minimum of water per unit of other components. Such machines are practically limited to concrete having a plasticity such that it gives a slump of more than 1%". The object of my invention is to provide a method and apparatus capable of finishing concrete having a maximum of aggregate and a minimum of water, to the desired degree of smoothness, in a single pass.

In accordance with my invention 1 eliminate entirely the reciprocating screed as a means for conditioning, compacting or smoothing the concrete. In a traveling unit including a wheeled frame adapted to move on road rails, I provide vertically oscillating tampers both to push forward surplus concrete and tocondition and pack concrete in place against a moving steadily forward form, which prevents all uplift of concrete behind the tampers. This form is supported by the wheeled frame. The unit carries sources of motive power for driving it and the reciprocable tampers. A wide range of adjustment of the tampers and form is obtainable with my construction and numerous other features and advantages thereof will appear as the detailed description proceeds, the novel features being pointed out specifically in the appended claims.

A present preferred embodiment of the invention is illustrated in the accompanying drawings although it will be understood that it may be otherwise embodied or practiced in the scope of my broader claims. In the drawings:

Figure 1 is a plan view of the apparatus;

Figure 2 is a sectional view taken along the line II--II of Figure l with parts broken away;

Figure 3 is a side elevation;

Figure 4 is a view partly in section along the line IVIV of Figure l;

Figure 5 is a partial side elevation of the structure shown in Figure 4;

Figure 6 is a partial plan view of a modified construction;

Figure '7 is a side elevation thereof;

Figure 8 is a sectional view taken substantially along the line VIl1-'-VIII of Figure 7; 1

Figure 9 is a partial front elevation of a modifled tamper;

Figure 10 is an end elevation with parts in section;

Figure 11 is a diagrammatic view of the behavior of the concrete in front of the advancing tampers; 1

Figure 12 is a vertical sectional view through a modified form of tamper showing -the tamper oscillating mechanism in greater detail; and

Figure 13 is a partial elevation of a tamper showing a detail.

To facilitate an explanation of the apparatus of my invention, the description thereof will be divided into sections each referring particularly to one portion of the apparatus as follows:

1. The car and its drive.

2. The form and its adjustable supporting means. I

3. The tampers and their reciprocating mechanism. I

4. The side wings or guides.

5. Modified forms and other details.

The car and its drive Referring particularly to Figures 1 through 5 for the present, the apparatus of my invention comprises a frame It) having front and rear channels H and I2 and side members composed of spaced channels l3. The side members are secured to the front and rear members in any convenient manner. as by welding. Bearing brackets l4 extend downwardly from the side members adjacent the front and rear channels. Shafts l5 journaled in bearings provided by the brackets carry wheels l6 adapted to roll on road rails l1 which serve as the forms for the slab to be finished. The shafts l5 are provided with sprockets l8 so that the wheels l6 may be oper ated by a chain drive from a power source on the car, specifically, the internal combustion engine l9.

Auxiliary side channels 20 are supported'on the channels l3. Transverse channels 2| are supported on the channels 20. A longitudinal channel 22 has its rear end disposed on the upper flange of channel l2 and itsv forward end secured to the lower flanges of channels 2|. The engine I 9 is supported on the channel 22 and on the box 21 is supported on transverse channels 28 and 29. The lefthand ends of the channels are secured to one of two. longitudinal channels 36 mounted similarly to the channel 22. The righthand end of the channel 29 is secured to the channel 22 and the righthand end of the channel 28 to a longitudinal channel 3| extending between and supported by the channel l2 and the channel 29. The gear box 21 is provided with a shaft 32 having a sprocket and gear loose thereon and a jaw clutch 33 by which either the sprocket or the gear may be secured to the shaft. Thus the shaft 32 may be driven from the shaft 21 alternately by the gear drive 34 or the .chain and sprocket member 4| fixed relative to but rotatable on the shafts 36 and cooperating members 42 movable along the shafts 36 but non-rotatable relative thereto. By means of suitable operating levers, either or both of the shafts 36 may be driven from the shaft 32 by the chain and sprocket drive 43 connecting the shaft 32 and the fixed member 4| of the clutch 40.

The shafts 36 are provided at their outer ends with driving sprockets 44. These sprockets co-- operate with chains 45 trained over the sprockets I8 and suitable idler sprockets 46 joumaled betweenthe side channels l3, to drive the wheels l6. This arrangement of driving connections makes it possible to drive all four wheels in either direction, or only the wheels on one side of the car. This latter is of advantage in working on curves. 7

The form The form comprises a generally fiat sheet or plate 50 having its leading edge flanged upward and provided with transverse stiifening channels 5i The plate 50 is also provided with longitudinal stiffening channels 52. ported on aframe movable relative to the car frame H, l2, I3 and composed of longitudinal channels 53 and transverse channels 54 secured to the lower flanges of the channels 53. The form plate 50 is suspended from the transverse channels 54 by hanger bolts 55 which are slidable through aligned holes in the flanges of the channels. The bolts 55 are secured to the plate 58 head downwardly by yokes 56 welded or otherwise secured to the channels 5|. The bolts 55 are threaded through nuts 51 welded to the upperflanges of the channels 54. Nuts 58 are welded to the extreme upper ends of the bolts 55. By applying a wrench to the nuts 58, the various bolts 55 may be adjusted to give the form plate 50 the desired contour. The channels 5| permit slight bending of the form as a result of the adjustment ofthe bolts 55.

The outer edges of the form plate 56 are held in engagement. with the road rails I! by the hold-down bolts 59 which pass through aligned holes in the channels 54 in the same manner as the bolts 55. The bolts 59 are provided with .coil springs 60 compressed between the lower flanges of the channels 54, and washers 6| and nuts 62 threaded on the bolts 59. Check nuts 63 are threaded on the upper ends of the bolts 59 to limit downward movement of the edges of the form.

Spaced channels 64 extend transversely of, the car frame ahead of the channels 5|. The ends of the channels 64, however, are not secured to the side channels l3 of the car frame but merely rest thereon. The upper flanges of the longitudinal channels 53 are secured to the lower flanges of the transverse channels 64. By raising and lowering the channels 64, however, the form plate 50 may An actuating The form is supbe adjusted vertically. The upward movement of I of the channels I3. Independent means are providedfor raising and lowering opposite sides of the form frame. A description of one of the ad-. justing means will therefore sumce for both. Short channels 85 extending between channels 2i provide bearings 88 for a short transverse shaft 81. Between the two outer bearings, the shaft 81 is provided with a worm wheel 88. A worm 89 on a vertical shaft I8 is in mesh with the worm wheel 68. The shaft I8 is journaled in a bearing carried on plate H extending between the channels 2 I and a thrust bearing I2 carried on a plate extending between the channels I3. The shaft 18 is provided with a hand wheel I3.

The shaft 61 is also provided with an eccentric I4 between the two inner bearings 88. A link I5 connects the eccentric I4 and one of thelongitudinal channels 53. On rotation of the hand wheel 13, therefore,- the shaft 61 turns and the resulting rotation of the eccentric I4 raises the link I5 and one side of the form frame.

Vertical movement of the form frame in the car frame is guided by dowel pins IS. The dowel pins I8 pass through aligned openings in plates 11 secured to the upper and lower flanges of the channels 53 and similar aligned openings in plates I8 secured to the upper and lower flanges of channels I3.

The form frame comprising the channels 53 and 54 is shown in Figures 2 and 3 in its lowermost position. The upward movement of the frame, as before stated, is limited by engagement of the frame flanges of the channels 54 with the lower flanges of the channels I3. Downward movement of the rear end of the form frame is limited by plates I9 secured to the upper flanges of the channels 53 and over-lapping the lower flanges of the channels 28.

Upward pressure of the concrete on the form plate is transmitted directly to the channels 54, the channels 53 and then through the links I5 and eccentric I4 to the channels 2| which are flrmly secured to the car frame comprising the channels II and I3. The entire weight of the apparatus is thus effective to resist the upward pressure of the concrete; While the frames of the car and form are relatively rigid, they may be so designed as to permit slight warping so that all the wheels I6 will have contact with the road rails II, even though the latter are not precisely horizontal or parallel. I traction of the driving wheels on the road rails is the only force to overcome the friction between the form and the concrete being finished, which may amount to several thousand pounds. In order to transmit force to overcome this friction directly'from the car frame to the form, I provide .bracket plates 88 extending downwardly from slab and the channels 54 need, therefore, only be rigid enough to withstand the bending moment developed by the upward pressure of the concrete.

The tampers and their reciprocating mechanism The form which has been described in detail does not operate in the manner of a screed to This is highly desirable because the push concrete in front of it but serves only to prevent upflow of the concrete already in place. Tampers are disposed immediately ahead of the form whereby the concrete is agitated into its most plastic condition as the leading edge of the form passes over it. The tampers also pack the concrete firmly under the form and between the road'rails. The length of the form is such that concrete cannot flow under it as a result of the agitation produced by the tampers. As a matter of fact, the form is of such length that the concrete is quite solid at the trailing edge, being preferably firm enough to support "the weight of a man without denting. The concrete is plastic only for a short distance back of the leading edge of the form.

Tampers are disposed end to end and are supported from the channels 64 for oscillation. The tampers are of box-like construction having closed bottoms, and reenforcing webs 86 between the'front and rear walls. The forward lower edge of each tamper is rounded.

Each tamper has at least one pair of spring suspensions 81 for supporting it from the channels 64. Each of these suspensions comprises a rod 88 the lower end of which is loosely secured to a bracket 88' fixed in the structure of the box forming the tamper, by any convenient'means such as a pin and slot connection. The rod 88 passes through a hole in a plate 89 secured to the channels 84. Springs 98 and 9| on the rod 88 are compressed between the plate 89 and washers 92 backed up by nuts 93 whereby the tamper itself -is resiliently supported on the channels 64.

As shown in Figure 3, the tampers extend upwardly between the channels 64 and are provided with brackets 94 whereon is mounted mechanism 95 for vibrating oraoscillating the tamper. This mechanism, as shown in Figure 12, consists of a housing 96 secured to the brackets 94, having a shaft 91 journaled therein in suitable bearings, and an eccentric weight 98 secured to the shaft. Vibrating mechanism of this type is more fully described and claimed in the copending application of Harold E. McCrery Serial No. 704,396. It will be apparent, however, that rotation of the shaft 91 will cause vibration of "the tamper 85 by reason of the eccentric mounting of the weight 98. The eccentricity of the weight is adjustable. The oscillating mechanisms 95 are driven through extensible shafts 99 connected thereto and to driving shafts by'universal joints I88. The driving shafts are shown at I8I, being journaled in suitable bearings I82 carried by the channels 2|. Power is supplied. to the shafts I8I from any convenient source such as an internal combustion engine I83 mounted on channels 38. The engine has an integral clutch and operating shaft I84 therefor. The engine is coupled to an intermediate shaft I85 journaled in bearings supported in the same manner as those shown at I82. Chain and sprocket drives I88 connect the shaft I85 with the two adjacent shafts I 8|. A supplementary chain and sprocket drive I81 connects the third shaft IN to one of those directly connected to the shaft I85. The speed of the engine may be varied by the usual means, to produce the desired agitation or conditioning of the them, as shown in Figure 11, reciprocate vertically. Sufficient clearance between adjacent tampers and between the tampers and the road rails is provided so that it is not necessary that the tampers operate in synchronism.

Figure 11 indicates diagrammatically the manner in which the concrete piles up in front of the tampers. The dotted line I09 indicates the outline of the mass of concretepushed ahead of the tampers in normal operation. Due to the rapid vibration of the tampers, the concrete between the tampers and dotted line H is made: semifiuid, in which condition it will readily flow under the form 50. If the speed of forward movement of the machine is reduced, concrete will be made fluid within the zone indicated by the dotted line III. Conversely, if the-speed of the machine is increased the zone will approach the tampers as indicated by the dotted line H2. The degree of agitation is preferably so controlled that the concrete under the form is plastic back approximately as far as the dotted line H3 and no farther. By utilizing the provisions for varying the speed or amplitude of vibration imparted to the tampers, the machine may be adapted for handling concrete of various degrees of plasticity. Normally the vibrations of the tamper are rather small in amplitude, say between and 1 6. The normal position of the tampers relative to the form may be controlled by adjusting the nuts 93, and the inclination of their bottoms to the horizontal changed to suit various slab contours. Ordinarily the bottoms of the tampers should be at about the same level as the bottom of the form.

The side wings or guides Side guides H are carried in front of the machine frame, the forward edges being notched to receive the rails H on which the guides slide. At their rear edges, the guides have pins I I5 slidable in slots in brackets II! which support the guides against outward thrust as shown in Figures 1 and 2. The guides extend inwardly of the inner bearing brackets supporting the wheels I5. When not in use, the guides may be raised by operating levers H8 secured to shafts carrying eccentrics H9. Links I20 connect the eccentrics to the guides.

Modified forms and other details Figures 6, '7, and 8 show a modified form of tamper I20 which extends substantially the full width between the road rails IT. The tamper I20 is otherwise similar to the tamper 85. It is carried on spring suspensions I2I. Each suspension I2I includes a yoke I22 carried on the channels 84. A plate I24 extending across the top of the tamper has bolts I25 welded to the lower side thereof whichextend downwardly through holes in the bottom inturned portions of the yoke I22. Supporting springs I26 are compressed between the inturned bottom portions of the yoke and washers I2'I backed up by nuts I28. Springs I29 are compressed between the plate I24 and washers welded to the lower ends of bolts I25a threaded through tapped holes in the yoke I22 and extending downwardly therefrom in line with the bolts I25.

Vibrating mechanisms I30 similar to those shown in 95, are mounted on the plates I24 carried by the tamper and are coupled to an intermediate drive shaft I3I journaled in bearings I32 supported on the cross plates extending between the channels 64. The shaft I3I is connected to the mechanisms I30 through extensible shafts and universal joints as described in connection with the modification of Figures 1 through 3.

Since the two vibrating mechanisms I30 are mounted on the same tamper, they should be operated in synchronism to avoid excessive stress in the tamper. The shaft I3I is driven through a belt drive I33 and another intermediate shaft I34 by an engine I35, corresponding to the engine I 03 mounted somewhat differently. The remaining details'of the structure of Figures 6 through 8'correspond to those of the modification of Figures 1 through 3 with one exception, viz., that the form 50' and the tamper I20 (see Figure 7) are provided with groove casting ribs I36 and I 31. These ribs are secured to the tamper and form in any convenient manner, for instance, by lugs I38 extending upwardly through slots in the tamper and form, and wedges I39 extending through the lugs. By this means, it is possible to form a continuous groove extending along the slab, where such is desired.

Figures 9 and show a further form of tamper having a bottom plate I40 adapted to traverse the sub-grade. The plate I40 is supported by edgewise plates I4I extending upwardly therefrom. The tamper is completed by front and rear walls I4Ia and I4Ib. This type of tamper, however, is limited to pavement having no reenforcing steel or other inclusions which would prevent it from passing through the concrete.

Figure 12 illustrates in addition to the details of the operating mechanism 95, a further modified form of tamper I42. This tamper is composed of flat and bent plates assembled and secured together in the manner shown.

Rgad finishing machines often have provisions permitting them to be adjusted for various road gauges. While such means have not been shown herein, they may be provided to accommodate changes in road width, for example, on curves, and if so, it is desirable that the concrete be subject to the action of the tampers throughout the road width. Forms such as that shown at 50 may be provided. in various widths depending on the adjustment provided for the supporting wheels. Figure 13 illustrates means by which the tamping effect can be obtained throughout the road width where the latter is greater-than the total width of the tampers 85. As shown in Figure 13, the tampers 85 nearest the road rails I! are provided with extensions I45. These extensions are preferably of hollow box form and have a rounded front lower edge. The extensions may be secured to the tampers 85 by bolts I48. The extensions I45 must clear the tops of the rails I1 and as the bottoms of the tampers 85 normally are below the tops of the rails, the relative positions of the tampers and extensions are asshown in Figure 13.-

The extensions. oscillate with the tampers, however, and ensure proper aigitation or conditioning of the concrete between, the ends of the tampers 85 and the rails IT. The form 50 serves to hold the concrete in position after tamping, in the manner already described, until it becomes nonplastic.

It will be apparent from the foregoing description that the invention is characterized by numerous advantages over finishing machines previously known, in thatit makes possible the finishing of a concrete slab, for example, in a single pass, to a true surface, using concrete having "less plasticity, (that is, having more aggregate or less water) than it has been possible to finish with machines of other types. The invention makes possible for the first time the satisfactory finishing of the upper surface of a flat slab formed of concrete having a low plasticity.

In contrast to the effect of the screed of an ordinary finishing machine, the form 50 exerts no smoothing or troweling action whatever, such as'is exerted by a plasterer in smoothing a wall surface. It is merely a sliding form. The concrete is packed against it when placed and each particle retains exactly the same position that it occupies when first placed against the form, except insofar as it is agitated by the tamper in front of the form until the machine is moved forward sufficiently far to prevent such agitation from being effective.

The construction is such that practically no vibration is communicated by the tamping device to the form itself. Any agitation thatis communicated to the form is transmitted through the concrete. The form must not be considered as a member to work upon the concrete but merely as a member to hold the concrete in place.

The invention avoids the difficulty inherent in the use of a reciprocating screed and operates to compact as well as shape the concrete in a single pass. This is what makes it possible to reduce the amount of water or increase the amount of aggregate in the concrete. By avoiding a reciprocating screed, transverse forces on the road rails are eliminated. Such forces are the cause of rail settlement and m s-alignment. Reciprocating screed machines, furthermore, are limited to crowns which are circular arcs, as they will not function satisfactorily on other types of curves. invention. The casting of longitudinal grooves is facilitated and eliminates the necessity of cutting such grooves after finishing.

Since the invention makes it possible to finish a slab in one pass leaving the slab less plastic than has heretofore been possible, cements characterized by quick setting may be employed. The advantage of such cements is obvious.

Another advantage of the invention is that it does not interfere with the present methods of placing concrete, reinforcing steel, or expansion joints.

The entire weight of the apparatus is available to increase the traction of the driving wheels along the road rails.

The form may be adjusted to a variety of contours or crowns and one side may be raised or lowered independently of the other. Although the form engages the road rails, it issupported from the car, reducing friction between the form and the rails. The form is carried directly on the car and the upward pressure of the concrete in the slab is transmitted directly to rigid sustaining members. J

In the operation of the apparatus, the can crete being finished is rendered plastic for only a short distance behind the leading edge of the form and the slab is firm enough to support a mans weight after the form has passed over it. Machines known previously require concrete so plastic that it will not support a man from 50 to 300 feet behind the machine.

The spring supports for thetampers prevent noisy operation but the springs are not materially stressed because of the small amplitude of the vibrations. Since each tamper has two independent suspensions, the opposite ends may be adjusted to different levels.

The machine is also capable of being used effectively to place concrete of the plasticity hitherto in common use, or to compact and spread such road materials as gravel orcrushed stone.

Although I have illustrated and described This limitation is avoided by the present herein only a preferred practice and form of my invention, it will be understood that the invention may be practiced and embodied otherwise than as shown without departing from the spirit thereof or the scope of the appended claims.

I claim:

1. A tamper comprising a bottom plate, web plates extending upwardly therefrom in spaced relation, and means joining said web plates at a level above said bottom plate.

2. In a finishing machine for road construction, a car adapted to run on road rails, members extending transversely of the car, capable of being raised or lowered with respect thereto, tampers below said transverse members, means for resiliently supporting said tampers from said members, and means for oscillating said tampers as said car travels along said rails.

3. In a finishing machine for road construction, a car, parallel transverse members supported on the car and capable of being raised and lowered with respect thereto, a tamper member between said transverse members, means for resiliently supporting said tamper member from said transverse members, said means being adjustable to vary the elevation of the tamper, and means for oscillating said tampers as said car travels along said rails.

4. In afinishing machine for road construction, a car, parallel transverse members supported on the car and capable of being raised and lowered with respect thereto, a tamper member between said transverse members, means for resiliently support'ng said tamper member from said transverse members, oscillating means mounted on said tamper, and means mounted above said transverse supporting members for driving said oscillating means, and means for oscillating said tampers as said car travels along said rails.

5. The process of placing concrete containing so little water or so much coarse aggregate as not to be plastic under steadily applied pressure, which consists in subjecting the mass to very violent vibratory agitation immediately in front of a forwardly moving form member so as to render it pseudo-fluid immediately beneath the forward form edge due t-o the violent agitation of its particles, holding the form down against the upward pressure of the concrete, and controlling said agitation so that said fluidity does not extend to the extremity of the form farthest from the front where said agitation is applied, thereby leaving a compact non-plastic surface immediate ly behind said advancing form.

6. Paving apparatus comprising a car including-a wheeled frame adapted to traverse side rails, a tamper mounted on the frame, for vertical movement, a plate extending between said rails from a point immediately behind the tamper and adapted to serve as a form for concrete tamped thereunder, and means including a rigid frame supported on the car for preventing said plate from rising under the pressure of said concrete.

7. Paving apparatus comprising a car, a tamper mounted adjacent the front of the car for vertical movement, a rigid frame behind the tamper, a packing plate carried on said frame adapted to provide a surface against which concrete may be packed by said tamper, and means on said car preventing uplifting of said plate and frame under the pressure applied to the concrete by the tamper.

8. In a finishing machine for concrete roads, a car, a rigid frame supported by said car and vertically adjustable with respect thereto, in

combination with a tamper resiliently supported from said frame, said tamper comprising a deep trough-shaped structure with a bottom plate for acting on concrete beneath it and a front plate for pushing concrete ahead of it, rotary weights for imparting'tamping motion with a vertical component at the tamper bottom, and drive mechanism for said rotary weights secured to the frame upon which the tamper is resiliently mounted.

9. In a paving apparatus, the combination with a car adapted to traverse side forms or road rails, tamping mechanism movably carried on said car, of a packing plate immediately behind said tamping mechanism, and a rigid frame mounted on the car, means for adjusting the frame vertically of the car said plate being secured to said frame and said mechanism including a vibrating tamper immediately in front of said plate having a substantially horizontal surface efiective to agitate concrete into position against the underside of said plate and a substantially vertical surface effective to force surplus concrete ahead of said tamper.

10. The apparatus as defined by claim 9 characterized by means for yieldingly urging the outer edges of said plate into engagement with said rails.

11. The apparatus as defined by claim 9 characterized by means for adjusting one side of said frame vertically independently of the other end.

12. The apparatus as defined by claim 9 characterized by means for adjusting one side of said frame vertically independently of the other end, and means guiding movement of said frame relative to said car.

13. The apparatus as defined by claim 9 char acterized by-means extending downwardly from said car for withstanding the horizontal thrust on said'plate.

14. The apparatus as defined by claim 9 characterized by said tamping mechanism including a vertically reciprocable member floatingly supported on said car, and means for vibrating said member. I

15. The apparatus as defined by claim 9 characterized by side guides carried on said car ahead of said tamping mechanism and overlying said rails.

16. The apparatus as defined by claim 9 characterized by side guides carried on said car ahead of said tamping mechanism and overlying said rails, and means on the car for raising said guides out of their normal operating position.

17. Paving apparatus comprising a'car adapted to travel on road rails, a form below the car supported therefrom, providing a surface against the under side of which concrete may be packed, adjustable means supporting the form at a plurality of points whereby the contour of the form may be varied, and means on the car for preventing uplift of the form without lifting the car.

18. In a paving apparatus, the combination with a car adapted to travel on road rafls, of a flexible form below the car, adjustable supports forthe form extending downwardly from the car, and means on the car for opposing upward thrust on the form.

19. Paving apparatus comprising a car, a vertically vibrating levelerand tamper mounted adjacent the front of the car, a packingplate immediately behind the tamper adapted to provide a surface against which concrete may be packed by said temper, and means for rigidly securing the packing plate tothe car so as to resist the upward pressure of the concrete produced by the tamper.

20. A method of finishing the surface of a concrete slab including the steps of depositing concrete of relatively harsh consistency between side forms, tamping the concrete locally from above until it is rendered temporarily fluid, simultaneously pushing surplus concrete ahead of the point of tamping, and confining the concrete immediately behind the point of tamping against upward fiow until the temporary fluidity ceases.

21. A tamper for a concrete road finishing machine, comprising a trough shaped member of sheet metal having two substantially vertical sides of considerable depth relative to its width, a substantially horizontal bottom plate for working on concrete beneath it and a substantially vertical front plate for pushing concrete ahead of it, with bearings for a horizontal shaft firmly secured to upper portions of both of the vertical sides and a shaft in said hearings to receive power for revolving weights to actuate the tamper, said power being transmitted to said shaft by substantially horizontal I mechanical driving mechanism from a power unit mounted independently of said tamper.

22. Paving apparatus comprising a car, a

tamper, a spring suspension supporting the tamper from the car, and means for adjusting the spring of said suspension bodily relative to the tamper whereby the initial position of the tamper relative to the carJnay be varied.

v 23. In a road finishing machine, a car adapted to travel on side forms, a top form plate rigidly secured to said car when in operative position so as to be held down by the weight thereof and extending in a substantially horizontal plane between said side forms, a tamper immediately in front of said top form efiective to condition concrete as it is being placed adjacent the leading edge thereof and force it under pressure against the under side thereof, rotary weight mechanism for actuating the tamper, means for moving the car forward at a predetermined speed, and a variable speed drive for said mechanism whereby to vary the fluidity of the material during the process of placing, due to the agitating effect of the tamper mechanism.

24. In a method of paving, the steps including distributing paving material between side forms, moving a top form thereover, violently tamping the material immediately in front of the top form until it is rendered temporarily fluid, applying to the top form a downward force in addition to its own weight to hold it against vertical movement under the upward pressure of said material, and maintaining engagement of said top form with the material until said material is nonplastic when uncovered by the form.

WILLIAM MAYO VENABLE. 

